1. Field of the Invention
The present invention relates to an ink composition for ink-jet textile printing. More particularly, it relates to an ink-jet textile printing ink, suited for textile printing on woven fabric or nonwoven fabric mainly composed of cellulose fibers such as cotton, capable of being dyed with a reactive dye, or mixed woven fabric or mixed nonwoven fabric comprised of any of these fibers and other synthetic fibers. The present invention also relates to an ink-jet textile printing process making use of such an ink.
2. Related Background Art
Screen textile printing and roller textile printing are presently prevaling as textile printing. These methods, however, are not suited for the multi-item and small-quantity production and cannot quickly respond to fashion with ease. Accordingly, there is a recent demand for establishing electronic textile printing systems that require no printing plates. To answer such a demand, a number of proposals have been made on textile printing carried out by ink-jet recording, which increasingly attracts expectations from various fields.
Ink-jet textile printing inks are required to have the following performances.
(1) They impart densities sufficient for color formation.
(2) They cause no clogging of ink ejection orifices or ink passages of a head.
(3) Inks quickly dries on cloths.
(4) They less irregularly run on cloths.
(5) During storage, they undergo no changes in their physical properties and are free from precipitation of solid matters.
(6) They cause no changes in ejection performance even in running over a long period of time. In particular, in the method in which a change in volume by the action of heat energy is utilized to eject ink, as disclosed in Japanese Patent Application Laid-open No. 54-59936, they cause no deposition of foreign matters on a heater that provides the heat energy or cause no break of the heater when cavitation occurs during debubbling.
In order to satisfy these performance requirements, the following measures have been hitherto taken.
With regard to item (1), a measure commonly taken is that dyes are used in a high concentration to impart sufficient densities, which is essential particularly when small droplets of 200 pl or less are used or when cloths with a strong absorbing power are used. Inks used therefor, however, may become thick as a result of evaporation of ink from nozzle tips or cause precipitation of dyes, i.e., the solid matters, to often bring about the problem noted in item (2). Now, with regard to item (2), a measure has been taken such that polyhydric alcohols such as glycerol are added. When, however, a dye is in a concentration of 5% or more, there is no particular means that can be said to be perfect enough to solve the problem. Thus, no satisfactory results can be obtained except that the dye and a solvent are used in particularly unusual combination.
With regard to item (3), the water repellency of cloths has a great influence. There, however, is no particular problem when, for example, water-based inks are used on cloths mainly composed of cellulose fibers. With regard to item (4), a number of proposals have been already made. For example, addition of tannin to ink is proposed in Japanese Patent Application Laid-open No. 61-231289, and addition of a carboxylic acid group-containing polymer, in Japanese Patent Application Laid-open No. 62-283174. Both of them, however, cannot avoid the problem noted in item (2). With regard to items (5) and (6), problems are often ascribable to the structures of dyes, but have not been well settled since no detailed studies have been made.
As discussed above, some conventional techniques can provide measures by which some of the above performances required in ink-jet textile printing inks can be satisfied individually. Under existing circumstances, however, no textile printing ink and ink-jet textile printing process are known until now which can satisfy these performances at the same time and can solve such a series of problems.